Quantum dot solar cell

ABSTRACT

A solar cell is disclosed that may include a quantum dot, an electron conductor, and a bifunctional ligand disposed between the quantum dot and the electron conductor. The bifunctional ligand may include a first anchor group that bonds to the quantum dot and a second anchor group that bonds to the electron conductor. The solar cell may include a hole conductor that is configured to reduce the quantum dot once the quantum dot absorbs a photon and ejects an electron through the bifunctional ligand and into the electron conductor. The hole conductor may be a p-type polymer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Application Ser. No. 61/149,891 entitled “QUANTUM DOT SOLARCELL” filed Feb. 4, 2009, the entirety of which is incorporated hereinby reference.

TECHNICAL FIELD

The disclosure relates generally to solar cells and more particularly toquantum dot solar cells.

SUMMARY

The disclosure relates generally to solar cells. In an illustrative butnon-limiting example, the disclosure relates to a solar cell thatincludes a quantum dot layer, an electron conductor layer, an optionalbifunctional ligand layer that is disposed between the quantum dot layerand the electron conductor layer, and a polymeric hole conductor layerthat is secured relative to the quantum dot layer. The polymeric holeconductor layer may include a substituted quinoline moiety.

In an illustrative but non-limiting example, the disclosure relates to asolar cell that includes a quantum dot, an electron conductor and abifunctional ligand that joins the quantum dot and the electronconductor. The illustrative solar cell also includes a hole conductorthat is of the formula

where n is an integer ranging from about 6 to about 12.

In another illustrative but non-limiting example, the disclosure relatesto a solar cell that includes a quantum dot, an electron conductor and ahole conductor. The hole conductor may include a substituted quinolinemoiety. In some cases, a bifunctional ligand may be disposed between thequantum dot and the electron conductor. In this illustrative embodiment,the bifunctional ligand may be selected from the group of

The above summary is not intended to describe each disclosed embodimentor every implementation of the disclosure. The Figures and Descriptionwhich follow more particularly exemplify these illustrative embodiments.

BRIEF DESCRIPTION OF THE FIGURES

The following description should be read with reference to the drawings,in which like elements in different drawings are numbered in likefashion. The drawings, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of thedisclosure. The disclosure may be more completely understood inconsideration of the following detailed description of variousembodiments in connection with the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional side view of an illustrative butnon-limiting example of a solar cell; and

FIG. 2 is a schematic cross-sectional side view of another illustrativebut non-limiting example of a solar cell.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DESCRIPTION

The following description should be read with reference to the drawings,in which like elements in different drawings are numbered in likefashion. The drawings, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of theinvention. Although examples of construction, dimensions, and materialsare illustrated for the various elements, those skilled in the art willrecognize that many of the examples provided have suitable alternativesthat may be utilized.

FIG. 1 is a schematic cross-sectional side view of an illustrative solarcell 10. In the illustrative example shown in FIG. 1, there may be athree-dimensional intermingling or interpenetration of the layersforming solar cell 10, but this is not required. The illustrative solarcell 10 includes a quantum dot layer 12. Quantum dot layer 12 mayschematically represent a single quantum dot. In some cases, quantum dotlayer 12 may be considered as representing a large number of individualquantum dots. In the illustrative embodiment of FIG. 1, a bifunctionalligand layer 14 is provided, and may schematically represent a singlebifunctional ligand, such as those discussed below. In some cases,bifunctional ligand layer 14 may represent a large number of individualbifunctional ligands, with at least some of the bifunctional ligandswithin bifunctional ligand layer 14 bonded to corresponding quantum dotswithin quantum dot layer 12. The illustrative solar cell 10 of FIG. 1also includes an electron conductor layer 16. In some cases, electronconductor layer 16 may be an n-type conductor as discussed below. Theillustrative solar cell 10 may further include a hole conductor layer18. As discussed below, the hole conductor layer 18 may be a p-typeconducting electrode layer.

Quantum dot layer 12 may include one quantum dot or a plurality ofquantum dots. Quantum dots are typically very small semiconductors,having dimensions in the nanometer range. Because of their small size,quantum dots may exhibit quantum behavior that is distinct from whatwould otherwise be expected from a larger sample of the material. Insome cases, quantum dots may be considered as being crystals composed ofmaterials from Groups II-VI, III-V, or IV-VI materials. The quantum dotsemployed herein may be formed using any appropriate technique. Examplesof specific pairs of materials for forming quantum dots include, but arenot limited to, MgO, MgS, MgSe, MgTe, CaO, CaS, CaSe, CaTe, SrO,SrS,SrSe, SrTe, BaO, BaS, BaSe, BaTe, ZnO, ZnS, ZnSe, ZnTe, CdO, CdS,CdSe, CdTe, HgO, HgS, HgSe, HgTe, Al₂O₃, Al₂S₃, Al₂Se₃, Al₂Te₃, Ga₂O₃,Ga₂S₃, Ga₂Se₃, Ga₂Te₃, In₂O₃, In₂S₃, In₂Se₃, In₂Te₃, SiO₂, GeO₂, SnO₂,SnS, SnSe, SnTe, PbO, PbO₂, PbS, PbSe, PbTe, AN, AlP, AlAs, AlSb, GaN,GaP, GaAs, GaSb, InN, InP, InAs and InSb.

FIG. 2 is a schematic cross-sectional side view of an illustrative solarcell that is similar to solar cell 10 (FIG. 1). In some cases, areflective and/or protecting layer may be disposed over the holeconductor layer, as shown. The reflective and/or protecting layer may bea conductive layer. In some instances, the reflective and/or protectinglayer may include a Pt/Au/C film as both catalyst and conductor, butthis is not required. Alternatively, or in addition, a flexible andoptically transparent substrate, shown at the lower side (in theillustrated orientation) of FIG. 2, may be an electron conductor such asan n-type electron conductor. The n-type electron conductor may betransparent or at least substantially transparent to at least somewavelengths of light within the visible portion of the electromagneticspectrum.

In some cases, the n-type electron conductor may include or be formed soas to take the form of a structured pattern or array, such as astructured nano-materials or other structured pattern or array, asdesired. The structured nanomaterials may include clusters or arrays ofnanospheres, nanotubes, nanorods, nanowires, nano-inverse opals, or anyother suitable nanomaterials or shapes as desired. The quantum dots areshown electrically coupled to or otherwise disposed on the electronconductor. In at least some embodiments, the quantum dots may bedisposed over and “fill in” the structured pattern or array of theelectron conductor, as shown in FIG. 2.

It is contemplated that the electron conductor may be formed of anysuitable material. In some cases, the electron conductor layer 16 may bean n-type electron conductor. In some instances, the electron conductorlayer 16 may be metallic, such as TiO₂ or ZnO. In some cases, electronconductor layer 16 may be an electrically conducting polymer such as apolymer that has been doped to be electrically conductive or to improveits electrical conductivity.

As described with respect to FIG. 1, solar cell 10 may include abifunctional ligand layer 14. In some cases, bifunctional ligand layer14 may include a single bifunctional ligand or a large number ofbifunctional ligands. A bifunctional ligand may, in some cases, beconsidered as improving electron transfer by reducing the energybarriers for electron transfer. A bifunctional ligand may provide aconduit so that electrons which are ejected by the quantum dots cantravel to and through the electron conductor. A bifunctional ligand may,for example, secure the quantum dot relative to the electron conductorand/or any other related structure.

A variety of bifunctional ligands may be used. In an illustrative butnon-limiting example, a bifunctional ligand may be2-[2-ethoxycarbonylmethylsulfanyl)ethyl]-1,3-thiazolidine-4-carboxylicacid, which has the structure:

Another illustrative but non-limiting example of a suitable bifunctionalligand is 2-acetylamino-3-benzylsulfanyl propanoic acid, which has thestructure:

Another illustrative but non-limiting example of a suitable bifunctionalligand is isocysteine, which has the structure:

Another illustrative but non-limiting example of a suitable bifunctionalligand is 2-[(2-oxothiolan-3-yl)carbamoylmethylsulfanyl]acetic acid,which has the structure:

Another illustrative but non-limiting example of a suitable bifunctionalligand is phytic acid, which has the structure:

Another illustrative but non-limiting example of a suitable bifunctionalligand is pentetic acid, which has the structure:

As discussed with respect to FIG. 1, the illustrative solar cell 10 mayinclude a hole conductor layer 18. A variety of hole conductor materialsare contemplated. For example, hole conductor layer 18 may be formed ofa p-type electrically conductive polymer. In some instances, holeconductor layer 18 may be formed of or otherwise include:

as a repeating unit, where n is an integer ranging from about 6 to about12. In some cases, such a material may be formed via a Williamson ethersynthesis process by combining an appropriate hydroxy-terminated alkylthiophene with 5-chloromethyl-8-hydroxy quinoline in the presence ofsodium hydride.

Another illustrative but non-limiting example of a polymeric materialsuitable for forming hole conductor 18 may be formed by combining poly(3,6-hydroxyhexyl thiophene) with 5-chloromethyl-8-hydroxy quinoline inthe presence of sodium hydride to provide the following structure as arepeating unit:

Another illustrative but non-limiting example of a polymeric materialsuitable for forming hole conductor 18 may be formed by combiningpoly(3,11-hydroxyundecyl thiophene) with 5-chloromethyl-8-hydroxyquinoline in the presence of sodium hydride to provide the followingstructure as a repeating unit:

Another illustrative but non-limiting example of a polymeric materialsuitable for forming hole conductor 18 may be formed by combiningpoly(3,12-hydroxydodecyl thiophene) with 5-chloromethyl-8-hydroxyquinoline in the presence of sodium hydride to provide the followingstructure as a repeating unit:

A particular example solar cell may have the following structure: anelectron conductor including TiO2; a bifunctional ligand including2-[2-(ethoxycarbonylmethylsulfanyl)ethyl]-1,3-thiazolidine-4-carboxylicacid; CdSe and/or other quantum dots; and a hole conductor includingpoly (3,6-hydroxyhexyl thiophene) functionalized with5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand including2-acetylamino-3-benzylsulfanyl-propanoic acid; CdSe and/or other quantumdots; and a hole conductor including poly (3,6-hydroxyhexyl thiophene)functionalized with 5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand includingisocysteine; CdSe and/or other quantum dots; and a hole conductorincluding poly (3,6-hydroxyhexyl thiophene) functionalized with5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand including2-[(2-oxothiolan-3-yl)carbamoylmethylsulfanyl]acetic acid; CdSe and/orother quantum dots; and a hole conductor including poly(3,6-hydroxyhexyl thiophene) functionalized with 5chloromethyl-8-hydroxylquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand includingphytic acid; CdSe and/or other quantum dots; and a hole conductorincluding poly (3,6-hydroxyhexyl thiophene) functionalized with5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand includingpentetic acid; CdSe and/or other quantum dots; and a hole conductorincluding poly (3,6-hydroxyhexyl thiophene) functionalized with5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand including2-[2-(ethoxycarbonylmethylsulfanyl)ethyl]-1,3-thiazolidine-4-carboxylicacid; CdSe and/or other quantum dots; and a hole conductor includingpoly (3,11-hydroxyundecyl thiophene) with5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand including2-acetylamino-3 benzylsulfanyl-propanoic acid; CdSe and/or other quantumdots; and a hole conductor including poly (3,11-hydroxyundecylthiophene) with 5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand includingisocysteine; CdSe and/or other quantum dots; and a hole conductorincluding poly (3,11-hydroxyundecyl thiophene) with5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand including2-[(2-oxothiolan-3-yl)carbamoylmethylsulfanyl]acetic acid; CdSe and/orother quantum dots; and a hole conductor including poly(3,11-hydroxyundecyl thiophene) with 5-chloromethyl-8-hydroxyquinolineas pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand includingphytic acid; CdSe and/or other quantum dots; and a hole conductorincluding poly (3,11-hydroxyundecyl thiophene) with5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand includingpentetic acid; CdSe and/or other quantum dots; and a hole conductorincluding poly (3,11-hydroxyundecyl thiophene) with5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand including2-[2-(ethoxycarbonylmethylsulfanyl)ethyl]-1,3-thiazolidine-4-carboxylicacid; CdSe and/or other quantum dots; and a hole conductor includingpoly (3,12-hydroxydodecyl thiophene) with5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand including2-acetylamino-3 benzylsulfanyl-propanoic acid; CdSe and/or other quantumdots; and a hole conductor including poly (3,12-hydroxydodecylthiophene) with 5-chloromethyl-8-hydroxyquinoline, as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand includingisocysteine; CdSe and/or other quantum dots; and a hole conductorincluding poly (3,12-hydroxydodecyl thiophene) with 5-chloromethyl-8hydroxyquinoline, as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand including2-[(2-oxothiolan-3-yl)carbamoylmethylsulfanyl]acetic acid; CdSe and/orother quantum dots; and a hole conductor including poly(3,12-hydroxydodecyl thiophene) with 5-chloromethyl-8-hydroxyquinoline,as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand includingphytic acid; CdSe and/or other quantum dots; and a hole conductorincluding poly (3,12-hydroxydodecyl thiophene) with5-chloromethyl-8-hydroxyquinoline as pendant group.

Another particular example solar cell may have the following structure:an electron conductor including TiO₂; a bifunctional ligand includingpentetic acid; CdSe and/or other quantum dots; and a hole conductorincluding poly (3,12-hydroxydodecyl thiophene) with5-chloromethyl-8-hydroxyquinoline as pendant group. These are merelyexamples and are not intended to be limiting in any way.

The disclosure should not be considered limited to the particularexamples described above, but rather should be understood to cover allaspects of the invention as set out in the attached claims. Variousmodifications, equivalent processes, as well as numerous structures towhich the invention can be applicable will be readily apparent to thoseof skill in the art upon review of the instant specification.

1. A solar cell, comprising: a quantum dot layer comprising a pluralityof quantum dots; an electron conductor layer; a bifunctional ligandlayer disposed between the quantum dot layer and the electron conductorlayer; and a polymeric hole conductor layer secured relative to thequantum dot layer, the polymeric hole conductor layer comprisingmonomers having a substituted quinoline moiety disposed at a terminalend thereof.
 2. The solar cell of claim 1, wherein the bifunctionalligand layer comprises


3. The solar cell of claim 1, wherein the bifunctional ligand layercomprises


4. The solar cell of claim 1, wherein the bifunctional ligand layercomprises


5. The solar cell of claim 1, wherein the bifunctional ligand layercomprises


6. The solar cell of claim 1, wherein the bifunctional ligand layercomprises


7. The solar cell of claim 1, wherein the bifunctional ligand layercomprises


8. The solar cell of claim 1, wherein the polymeric hole conductor layercomprises

where n is an integer ranging from about 6 to about
 12. 9. The solarcell of claim 1, wherein the polymeric hole conductor layer comprises


10. The solar cell of claim 1, wherein the polymeric hole conductorlayer comprises


11. The solar cell of claim 1, wherein the polymeric hole conductorlayer comprises


12. A solar cell, comprising: a quantum dot; an electron conductor; abifunctional ligand disposed between the quantum dot and the electronconductor, the bifunctional ligand bonded to the quantum dot and theelectron conductor; and a hole conductor secured relative to the quantumdot layer, the hole conductor comprising

where n is an integer ranging from about 6 to about 12
 13. The solarcell of claim 12, wherein the bifunctional ligand comprises


14. The solar cell of claim 12, wherein the bifunctional ligandcomprises


15. The solar cell of claim 12, wherein the bifunctional ligandcomprises


16. The solar cell of claim 12, wherein the bifunctional ligandcomprises


17. The solar cell of claim 12, wherein the bifunctional ligandcomprises


18. The solar cell of claim 12, wherein the bifunctional ligandcomprises


19. A solar cell, comprising: a quantum dot; an electron conductor; abifunctional ligand disposed between the quantum dot and the electronconductor, the bifunctional ligand being selected from the groupconsisting of

and a hole conductor secured relative to the quantum dot, the holeconductor comprising a monomer having a substituted quinoline moietydisposed at a terminal end thereof
 20. The solar cell of claim 19,wherein the hole conductor comprises

where n is an integer ranging from about 6 to about 12.